Clark County Fire Chief Greg Cassell said it took firefighters about 30 minutes to gain control of the blaze that broke out on the 14th floor of The Cosmopolitan of Las Vegas hotel.

One person was taken to a hospital suffering from smoke inhalation, fire officials said, but nobody suffered any burns from the flames that ignited outside on the pool deck.

The fire was first reported around 12.15pm local time, with multiple emergency calls coming in.

The blaze quickly consumed pool cabanas, chairs and furniture said. At least 110 firefighters were on the scene to not only tackle the fire, but help with evacuations.

It is not clear if any guests will be displaced by the fire, Mr Cassell said.

No flames made it into the hotel, but smoke got into some floors above the 14th floor because the windows of some rooms were open. Firefighters are working with ventilation personnel to use temporary fans to get the smoke out.

It could be quite some time before the cause of the fire is determined, Mr Cassell said. Investigators are interviewing guests and going through mobile phone videos.

Julio Loredo of San Francisco was in his room on the 33rd floor of the neighbouring Vdara hotel when his room started to darken.

"We looked out the window, and there was ash hitting our window," he said.

He then looked out a hallway window, where he saw guests fleeing The Cosmopolitan pool deck.

"People were running. We could see small explosions," Mr Loredo said. "It was in less than a minute that it was completely engulfed."

He also saw people running out of the hotel doors and onto the Strip.

"I've never seen anything like it before. It was unbelievable," he said.